Conventional thrust reversers for aircraft gas turbine engines are provided for deflecting exhaust gases discharged from the engine in a generally forward direction upon landing of an aircraft for assisting in braking the aircraft. The thrust reverser is typically designed to translate from a stowed position, wherein it is aerodynamically blended with a conventional nacelle surrounding the engine, to a deployed position spaced rearwardly of the engine exhaust nozzle such that the exhaust gases are turned forwardly while avoiding back pressure in the exhaust gases which would affect performance of the engine.
Target-type thrust reversers for underwing or fuselage mounted engines typically include a pair of symmetrical deflector doors, or deflectors, for providing thrust reversal. In an overwing mounted gas turbine engine, conventional thrust reversers are typically unsymmetrical and must function within a relatively confined area between the engine and the wing. There are several types of conventional target-type overwing thrust reversers which utilize one or more deflectors and various actuators and linkages for positioning the deflectors between stowed and deployed positions.
The required travel of the deflector between the stowed and deployed positions is typically relatively large, thus requiring suitable actuators and linkages. Exemplary conventional actuators typically generate relatively large actuation forces and have relatively long strokes. This is generally undesirable since the actuation system is not compact and the degree of serviceability of the thrust reverser is relatively low in such embodiments.
In one embodiment of an overwing exhaust nozzle assembly, a stationary exhaust fairing defines the exhaust nozzle outlet and is disposed aft of the reverser deflector when stowed. Accordingly, an internally mounted reverser actuation system would necessarily have to extend through the exhaust fairing for operation, which is generally undesirable since a more complex actuation system would therefore be required.
Furthermore, in operation, the thrust reverser is typically deployed when an aircraft is landing and is rolling at relatively high speed. Therefore, it is subject to relatively high air velocity passing over the engine and wing which generates substantial aerodynamic pressure forces on the deflector which must be suitably accommodated for minimizing or preventing buffeting of the deflector during deployment. The forces due to the airflow over the engine during landing are in addition to the forces generated by the exhaust gases discharged from the engine exhaust nozzle against the deflector for thrust reversal, which must also be accommodated by the linkages attaching the deflector to the engine, nacelle, and/or wing.